Magnetic field straightener



Feb- 14, 1967 J. JAoUEN ETAL 3,304,523

MAGNETIC FIELD STRAIGHTENER Filed Sept. 28, 1964 FIGS Z QM. ATToRN y United States Patent O 3,304,523 MAGNETIC FIELD STRAIGHTENER Jean Jaouen and Philippe Martinot-Lagarde, Paris, France, assignors to CSF-Compagnie Generale de Telegraphie Sans Fil, Paris, France Filed Sept. 28, 1964, Ser. No. 399,555 Claims priority, application France, Oct. 4, 1963, 949,554 9 Claims. (Cl. 335-210) The present invention relates to the production of magnetic fields with an axis of revolution, and more particularly relates to corrective devices, so-called magnetic eld straighteners, intended to improve the linearity and homogeneity of these fields.

Magnetic fields with a symmetry of revolution are produced -with the `aid of solenoids or systems having permanent magnets, and it is known that, in practice, defects in construction of the assemblies alter substantially the desired symmetry .and the homogeneity of the realized fields. Things then are as if dissymmetric transverse components were superposed on the desired magnetic field.

These undesirable components may be strongly reduced with the aid of corrective devices, usually called field straighteners.

Magnetic fields thus corrected are utilized in a number of applications and make possible, in particular, the focusing of e-lectron beams in traveling wave tulbes in which one utilizes the exchange of energy between a microwave and an electron beam moving parallelly to the direction of propagation of the wave.

According to the known technique, as illustrated, for example, in U.S. Patent 2,942,141, the field straigteners are formed by a stack of magnetic washers with high permeability alternating with non-magnetic washers, disposed perpendicularly to the axis of the magnetic field t-o be corrected, the apertures of the washers forming a cylinder whose axis coincides with the axis of the magnetic field.

The present invention has for its object an improvement in the field straighteners of type described above and consists in modifying these devices by replacing therein each magnetic washer by two or more magnetic washers in the form of concentric rings, placed within the same plane and separated between one another lby non-magnetic rings.

This novel device permits to realize on magnetic fields having a symmetry of revolution, a considerably increased correction as compared to that obtained with the prior art devices for the lsame encumbrance. The improvement, verified experimentally, is also equally justified by calculations. Accordingly, it is an object of the present invention to provide a field straightener of the type described albove which considerably improves the corrective action thereof compared to the known prior art devices.

Another object of the present invention resides in the provision of a magnetic field straightener of the type described above which, for the same dimensions, yassures improved corrective effects.

A further object of the present invention resides in the provision of an improved magnetic field straightener which is easy to manufacture, simple to assembly and does not involve expensive parts.

These and further objects, features and advantages of the present invention wil-l become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one embodiment of a field straightener Aaccording to the present invention, and wherein FIGURE 1 is a longitudinal cross sectional view of a field straightener in accordance with the present invention;

3,304,523 Patented Feb. 14, 1967 FIGURE 2 is a cross sectional view taken along line II-Il of FIGURE l;

FIGURE 3 is a cross sectional view taken along line III-III of FGURE 1; and

FIGURE 4 is a partial sectional view of the invention in association with a solenoid.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts, reference numeral 1 designates therein a cylindrical permanent magnet of any conventional construction, on the inside of which is disposed a field straightener 2, composed of non-magnetic washers 3 alternating with washer sets, each comprising, in the same plane, three concentric magnetic rings 4, separated from one another `by non-magnetic rings 5.

The non-magnetic pieces are made, for example, of Bakelite, aluminum, etc. The washer 3 and the sets composed of annular washer parts 4 and 5, which separate the same, are disposed in planes perpendicular to the axis of the cylinder 1. The washers 3 and the smallest ones of rings 4 and 45 have apertures of the same diameter which form a cylinder coaxial with the magnet 1.

Retainer washers 6, fixed to the extremities of cylinder 1 by any Iappropriate means, serve to tighten and maintain in place the field straightener assembly.

With such a device, one finds a magnetic field channelized along the axis of the cylinder 1 and practically deprived of any dissymmetric radial component.

While we have shown and described one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art. For example, identical results will also be obtained if in the place of the permanent magnet, solenoids of conventional construction, such as solenoid 10 in FIG. 4, are utilized. Thus, it is obvious that the present invention is not limited to the details shown and described herein but is susceptible of numerous changes and modifications as known to a person skilled in the art, and we therefore do not wish to be limited to the described and illustrated details but intend to cover all such modifications thereof as are encompassed by the scope of the appended claims.

We claim:

1. In combination, a hollow means operable to produce a magnetic eld and a field straightener positioned within the hollow space of said means, said field straightener including ring-like elements of non-magnetic material alternating with ring-like sets, cach containing in a sulbstantially com-mon plane ring-like elements of non-magnetic material alternating with ring-like elements of high permeability magnetic material.

2. In combination, a hollow substantially cylindrical magnet and a field straightener positioned within the hollow cylinder, said field straightener including substantially ring-like elements of non-magnetic material alternating rwith substantially ring-like sets, each containing in a substantially common plane ring-like elements of nonmagnetic material alternating with ring-like elements of high permeability magnetic material.

3. In combination a solenoid and a field straightener positioned within the solenoid, said field straightener including substantially ring-like elements of non-magnetic material alternating with substantially ring-like sets, each containing in a substantially common plane concentric ring-like elements of non-magnetic material alternating with ring-like elements of high permeability magnetic material.

4. In a magnet structure having means for producing a magnetic field and a field straightener operatively associated with the magnet structure to enhance the linearity homogeneity of the field including Washer elements of non-magnetic material alternating with Washer elements of magnetic material, the improvement essentially consisting of washer structures forming said second mentioned washer elements, each including a plurality of Washer portions of non-magnetic material and of high permeability magnetic material, respectively.

5. In a magnet structure having means for producing a magnetic field `and a field straightener operatively associated with the magnet structure to enhance the linearity and homogeneity of the field including washer elements of non-magnetic material alternating with Washer elements of magnetic material, the improvement essentially consisting of Washer structures forming -said second mentioned Washer elements, each including a plurality of Washer portions of non-magnetic material and of high permeability magnetic material respectively,

the Washer portions being disposed in each of said second washer elements in a substantially common plane.

6. In a magnet structure having means for producing a magnetic eld substantially in an axial direction and a iield straightener operatively associated with the magnet structure to enhance the linearity and homogeneity of the field including washer elements of non-magnetic material alternating with washer elements of magnetic material, the improvement essentially consisting of `Washer structures forming said second mentioned Washer elements, each including a plurality of washer portions of non-magnetic material and of high permeability magnetic material, respectively,

the washer portions of a washer structure alternating in the radial direction.

7. In a magnet structure having means for producing a magnetic field yand a field straightener operatively associated with the magnet structure to enhance the linearity and homogeneity of the field including Washer elements of non-magnetic material alternating with Washer elements of magnetic material, the improvement essentially consisting of Washer structures forming said second mentioned `Washer elements, each including a plurality of concentric Washer portions of non-magnetic material and of high permeability magnetic material respectively,

Iand the Washer portions of a Washer structure being of complementary shape. 8. In a magnet structure having means for producing a magnetic field and a field straightener operatively asso- 5 ciated with the magnet structure to enhance the linearity and homogeneity of the field including washer elements of non-magnetic material alternating with Washer elements of magnetic material, the improvement essentially consisting of Washer structures forming said second mentioned washer elements, each including a plurality of Washer portions of non-magnetic material and of high permeability magnetic material respectively,

the Washer portions being disposed in a substantially `common plane,

and the Washer portions of a Washer structure being of complementary shape.

9. In a magnet structure having means for producing a magnetic field substantially in an yaxial direction and a field straightener operatively associated with the magnet structure to enhance the linearity Iand homogeneity of the field including washer elements of non-magnetic material alternating with washer elements of magnetic material, the improvement essenti-ally consisting of Washer structures forming ysaid second mentioned Washer elements, each including a plurality of Washer portions of non-magnetic material and of high permeability magnetic material, respectively,

the washer portions Ibeing disposed in a substantially common plane,

the washer portions of a washer structure alternating in the radial direction, and the Washer portions of a washer structure being of complementary shape.

References Cited by the Examiner UNITED STATES PATENTS 2,925,517 2/1960 Glass S15- 3.5 2,939,995 6/1960 Danielson S15-3.5 2,942,141 6/1960 Cutler 315-35 BERNARD A. GILHEANY, Primary Examiner.

G. HARRIS, Assistant Examiner. 

1. IN COMBINATION, A HOLLOW MEANS OPERABLE TO PRODUCE A MAGNETIC FIELD AND A FIELD STRAIGHTENER POSITIONED WITHIN THE HOLLOW SPACE OF SAID MEANS, SAID FIELD STRAIGHTENER INCLUDING RING-LIKE ELEMENTS OF NON-MAGNETIC MATERIAL ALTERNATING WITH RING-LIKE SETS, EACH CONTAINING IN A SUBSTANTIALLY COMMON PLANE RING-LIKE ELEMENTS OF NON-MAGNETIC MATERIAL ALTERNATING WITH RING-LIKE ELEMENTS OF HIGH PERMEABILITY MAGNETIC MATERIAL. 